a. Field of the Invention
The present invention pertains generally to couplers and more particularly to couplers that engage the inner surface of a pipe, driveshaft, or similar device for transmitting torque.
b. Description of the Background
In the plumbing trade, it is common to attach pipe together using a pipe thread that is tapered, such as the standard National Pipe Thread. These thread systems are designed so that the taper of the threads force the internal and external threads to seal against each other to effect a seal for the joint. The very nature of this coupling system is such that the plumber will apply as much force as possible to ensure a tight seal for the pipes being installed. Often, a compound or putty is applied to the threads at the time of installation, but this compound can harden over time or the pipes may corrode, sometimes making removal of the pipe much more difficult than the installation.
The use of tapered threads for joining pipes is a standard method for high-pressure pipes such as steam pipes, gas pipes, and pressurized water, just as examples. The tools required for cutting pipe and cutting threads are part of every plumber's arsenal of tools, since this type of plumbing is used in almost every home, commercial building, and industrial factory.
The plumber will generally install and remove threaded pipe using wrenches that grip the exterior of the pipe when turning. These wrenches fall into two general categories: those with steel or other metal gripping teeth, and those with a compliant webbing.
The wrenches with steel teeth, of which the common pipe wrench is an example, are adjusted to apply a gripping force to the pipe while the pipe is being turned. As the turning force is applied, the grip is increased, and the pipe is turned.
The wrenches with compliant webbing, such as a strap wrench, consist of a metal handle and a piece of webbing, one end of which is attached to the handle. The free end of the webbing is fed around the pipe to be turned and then through a feature in the handle. As the handle is turned, the handle pinches the strap against the pipe and tightens the strap while simultaneously turning the pipe. A strap wrench described above generally does not have the excellent gripping force of the common pipe wrench with steel teeth. The strap wrench takes a considerable amount of time to install and remove from a pipe before and after turning the pipe, especially when compared to a common pipe wrench.
The wrenches with steel teeth that grab the external surface of the pipe to be turned can destroy the external threads especially when short nipples are being turned by the wrench and insufficient unthreaded portions of the nipple are available to grip. Further, external pipe wrenches often leave unsightly and disfiguring teeth marks on the outer surface of the pipe. This is unacceptable for pipe that is, for example, chrome plated and is not hidden from view. An alternative solution to those problems is the use of compression couplings or other types of fittings to join the pipe sections. However, this is more expensive, and a much more time consuming alternative and is often less reliable.
Actual deformation of a thin wall pipe is possible when a common pipe wrench is used to remove an old, rusted section of the pipe. This is due to the crushing action of the opposing steel teeth across the diameter of the pipe. The same crushing of the pipe may occur when using a strap wrench, since the handle of the wrench presses directly on the pipe as it pinches the strap against the pipe.
Further, all wrenches that engage the external surface of a pipe require some amount of room around the pipe to effectively turn the pipe. For some wrenches, such as the conventional pipe wrench, the amount of room can be considerable, and there are others designed for use in a confined space. However, the wrenches designed for confined space often have severe limitations in terms of ease of use and gripping power, and they always require at least some access to the external portion of the pipe.
In addition to the limitation of requiring a considerable amount of room for operation, the common pipe wrench, the strap wrench, and most other devices for turning a pipe are unidirectional in their operation. In other words, the pipe wrench, when being used for turning the pipe, may only turn the pipe in one direction. In order to reverse the direction of turning, the wrench must be removed from the pipe and turned to grip the pipe from the opposite direction, and reinstalled onto the pipe.
External pipe wrenches also have limitations for assembly in production factory environments. In such environments speed is paramount. Since the common methods of turning a threaded component with a pipe wrench are slow and cumbersome, much time is wasted using conventional pipe wrenches. Designers of such articles, realizing the slow and cumbersome assembly of threaded pipe oftentimes revert to other more expensive types of couplings. The cost savings realized in using threaded pipe can be substantial since the threading operation can be simply automated in a machining step that only takes a few seconds for both the pipe and the article receiving the pipe. The cost of a separate coupling, including a fastener to engage the coupling, may be much more expensive than the threaded interface. In addition, the threaded interface may provide a more esthetic result.
For example, the assembly of articles such as furniture that use components that are cylindrical pipes, such a chrome pipes, may be difficult to assemble using standard pipe wrenches, without marring the exterior cosmetic surface. In addition, high-speed production in factories that assemble boilers, sprinkler systems and components, furnaces, and other systems that use threaded pipe can be substantially limited by the use of a standard pipe wrench. As pointed out above, pipe wrenches are slow and cumbersome, require extra room to maneuver and operate and are generally not effective in a high-speed factory assembly production operation.
Various types of internal pipe wrenches solve some of these problems. For example, U.S. Pat. No. 5,207,131 issued to Pool, et al. discloses an oil filter removal tool. The disadvantage of the Pool, et al. device is that it includes springs 44 that bias the jaws of 48, 50 in an outward direction so that the jaws 48, 50 have to be depressed and urged inwardly to be inserted into an oil pan filter cap. U.S. Pat. No. 3,902,384 discloses an internal pipe wrench that has a tapered actuation element that must be adjusted to engage the inner surface of the pipe. Again, this is time consuming and has potentially other numerous disadvantages. Internal pipe wrenches available from BrassCraft have an offset pivot shaft on which a collar is mounted so that the collar becomes offset as the collar rotates around the offset shaft. The offset shaft that causes the collar to become offset and engage the internal portion of the pipe causes the device to be off center so that high speed assembly or disassembly is not achievable using the BrassCraft tools. In addition, the collar constitutes a single piece and does not tend to engage the inner surface of the pipe or nipple well. In addition, the rotatable sleeve must be oriented in a vertically downward position in order to engage a pipe when employed in a horizontal or nearly horizontal position. In that way, gravity can cause the sleeve to rotate in sync to its lowest point to engage the internal surface of the pipe. Since the sleeve has to be at the bottom, this limits the ease of use of the device. Further, in vertical orientations, the BrassCraft device may fail to easily engage the inner surface of the nipple. Further, the sleeve, because of its small size, may deform the pipe and could egg the pipe especially when engaging thin wall pipe. Further, in vertical alignment applications the user's fingers may have to be used to orient the rotatable sleeve in the correct position in order to insert the brass craft internal pipe wrench.
It would therefore be advantageous to provide a coupler that can securely grip a pipe, driveshaft or other shaft (hereinafter collectively referred to as a “torque receptor”) from the inside without marring the outside, support a thin walled torque receptor such as a pipe so that the pipe does not deform while turning even under relatively high forces, be compact and able to work in extremely tight spaces, be simple and quick to use, insert, extract, be universal in direction, and aligned with the center axis of the torque receptor when engaged.